Ball screw



FIG. 1 is a left perspective view of a ball screw;

FIG. 2 is a right perspective view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a back view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a right side view thereof;

FIG. 7 is a top view thereof;

FIG. 8 is a bottom view thereof;

FIG. 9 is a cross-sectional view thereof taken along line X-X in FIG. 8; and,

FIG. 10 is a cross-sectional view thereof taken along line XI-XI in FIG. 8.

The broken lines in the drawings illustrate portions of the ball screw which form no part of the claimed design. 

CLAIM The ornamental design for a ball screw, as shown and described. 